Native and non-native species range expansions in mountains

Species are expanding their ranges towards higher elevations in response to global warming, human influence and through biological invasions. Range shifts present both risks and opportunities; on the one hand, the capacity to respond to changing environments by shifting their ranges is necessary for the long-term persistence of native species, especially within diverse mountain ecosystems. But on the other hand, range expanding species themselves (including alien invasive species) might be important agents of change and could negatively impact native biodiversity and ecosystem functioning. For instance, novel species migrating up from lower elevations may contribute to population declines of resident species or alter biogeochemical cycles or other ecosystem services like pollination. To anticipate and respond to these challenges and opportunities, we require both a process-based understanding of range expansions, and a shared understanding of this issue between researchers, natural resource managers and policymakers.